As we parted at the Natural History Museum in London, I asked Richard Fortey how science ensures that when one person goes there's someone ready to take his place. He chuckled rather heartily at my naiveté. 'I'm afraid it's not as if we have substitutes sitting on the bench somewhere waiting to be called in to play. When a specialist retires or, even more unfortunately, dies, that can bring a stop to things in that field, sometimes for a very long while.' And I suppose that's why you value someone who spends forty-two years studying a single species of plant, even if it doesn't produce anything terribly new?' 'Precisely,' he said, 'precisely.' And he really seemed to mean it.